Nowadays, an energy-saving promotion becomes increasingly active as a countermeasure against global warming that is one global environmental problem. Particularly, as to heating and cooling devices, a vacuum insulation panel having an excellent heat insulating performance is becoming increasingly common from the viewpoint of efficient use of heat. The vacuum insulation panel is formed such that: a core material, such as glass wool, which has a high gas-phase volume ratio to form fine air gaps, is housed in a gas barrier laminate film formed into a pouched shape; and the laminate film is sealed under reduced pressure. An air gap diameter of the core material is reduced smaller than a mean free path of a gas molecule under reduced pressure, which decreases a gas heat conduction component of the vacuum insulation panel. Particularly, an influence of a convection heat transfer component is negligible in the case that the air gap diameter is as extremely small as about 1 mm. Additionally, because an influence of a radiation component is extremely low around room temperature, a solid heat conduction component of the core material and the slightly remaining gas heat conduction component become dominant as the heat conduction component in the vacuum insulation panel. Therefore, the thermal conductivity of the vacuum insulation panel is considered to be extremely lower than that of other heat insulation panels.
However, when air invades gradually into the vacuum insulation panel through the laminate film, unfortunately the gas heat conduction component increases to gradually increase a thermal conductivity of the vacuum insulation panel. Here, proposed as a solution to this problem is that a gas adsorbing device as a component of a vacuum insulation panel is sealed together with a core material under reduced pressure, the gas adsorbing device being configured to store a desiccant and a Ba—Li alloy getter in an open-top container, made of a gas impermeable material, to form such a two-layer structure that the desiccant is located on an open portion side of the open-top container, and the Ba—Li alloy getter material is located on a seal portion side of the open-top container (see PTL 1, for example).
FIG. 13 is a longitudinal sectional view showing a gas adsorbing device of Conventional Example 1 disclosed in PTL 1. As shown in FIG. 13, a gas adsorbing device 21 of Conventional Example 1 includes: an open-top container 22 made of the gas impermeable material; a first pellet 23 made from powders of the Ba—Li alloy getter material by compression at pressures of about 30 to 1,000 bar and housed in a lower portion of the open-top container 22; and a second pellet 24 made from desiccant powders and housed in an upper portion of the open-top container 22 so as to completely cover the first pellet 23 from above (from the open portion side of the open-top container 22).
In the vacuum insulation panel in which the gas adsorbing device 21 of Conventional Example 1 is sealed together with the core material under reduced pressure, water (steam) in air that has entered the vacuum insulation panel is adsorbed when the air flows from the open portion of the open-top container 22 through the second pellet 24. Then, the air whose water (steam) has been adsorbed by the second pellet 24 flows to the first pellet 23 to be adsorbed by the first pellet 23.
As above, the gas adsorbing device 21 of Conventional Example 1 is configured such that the second pellet 24 constituted by the desiccant covers the first pellet 23 constituted by the Ba—Li alloy getter material from the open portion side of the open-top container 22. With this configuration, it is possible to suppress a phenomenon in which the getter material constituting the first pellet 23 adsorbs the water (steam) in the air, and this deteriorates an air adsorbing performance of the getter material soon. Therefore, the degree of vacuum in the vacuum insulation panel is considered to be able to be maintained.
In addition, proposed as another solution to the above problem is that a gas adsorbing device configured such that a gas adsorbing material is sealed under reduced pressure in a hardly-gas-permeable container is sealed under reduced pressure as a component of the vacuum insulation panel together with the core material, and the hardly-gas-permeable container is then opened (see PTL 2, for example).
FIG. 14 is a side view of a gas adsorbing device of Conventional Example 2 disclosed in PTL 2 when viewed from a direction perpendicular to both a longitudinal direction and thickness direction of the gas adsorbing device. FIG. 15 is a side view of the gas adsorbing device of Conventional Example 2 disclosed in PTL 2 when viewed from an aperture sealed with a sealing material.
As shown in FIGS. 14 and 15, a gas adsorbing device 25 of Conventional Example 2 is produced by the following producing method. First, a hardly-gas-permeable container 26 constituted by a hollow bottomed tubular metal member is prepared. The hardly-gas-permeable container 26 has one end that opens and the other end that is sealed, and a length of a body portion thereof extending from the one end to the other end is at least a larger one of the width of the one end and the width of the other end. Next, a gas adsorbing material 29 is filled in the hardly-gas-permeable container 26 through an aperture 27 of the hardly-gas-permeable container 26. Next, a narrow portion 26a where inner surfaces of the hardly-gas-permeable container 26 are located close to each other is formed in the vicinity of the aperture 27. Next, a sealing material 28 is provided at the narrow portion 26a. While reducing the pressure of the inside of the hardly-gas-permeable container 26 and the pressure of a space around the hardly-gas-permeable container 26, the sealing material 28 and the vicinity of the aperture 27 are heated such that the sealing material 28 melts to close a gap of the narrow portion 26a. The melted sealing material 28 having closed the gap of the narrow portion 26a is cooled down to be solidified. As a result, the vicinity of the aperture 27 (the gap of the narrow portion 26a) is sealed.
The gas adsorbing device 25 of Conventional Example 2 produced through the above steps is considered to be applicable to a device, such as a vacuum insulation panel, which is required to maintain the vacuum without causing the gas adsorbing material 29 to contact the air.